158 research outputs found
Electrochemical and Spectroscopic Study of Benzotriazole Films Formed on Copper, Copper-zinc Alloys and Zinc in Chloride Solution
The formation of protective layers on copper, zinc and copper-zinc (Cu-10Zn and Cu-40Zn) alloys at open circuit potential in aerated, near neutral 0.5 M NaCl solution containing benzotriazole (BTA) was studied using potentiodynamic measurements, electrochemical
impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The addition of benzotriazole affects the dissolution of the materials investigated. Benzotriazole, generally known as an inhibitor of copper corrosion, is also shown to be an efficient inhibitor for copper-zinc alloys and zinc metal. The effectiveness of inhibition
depending on the type of materials was compared. X-ray photoelectron spectroscopic results showed that the surface layer formed on alloys in BTA-inhibited solution comprised both oxide and polymer components. The formation of Cu2O/Cu(I)-BTA on
copper, mixed oxides/Zn(II)-BTA and Cu(I)-BTA on copper-zinc alloys and ZnO/Zn(II)-BTA polymer surface film on zinc provides an effective barrier against corrosion on materials investigated in chloride solution
ZasliŔevanje arhitekture [Interrogating Architecture]
Teresa Stoppani is an Italian architect who grew up in the Venezia-Giulia, not far from the Slovene border. After studying in Venice and Florence she continued her career of teaching and research in Great Britain. Her work is focused on architectural history, contemporary architecture and in particular on the role of critical theory in architecture today. She recently participated in the symposium On Power in Architecture, organised by the Igor Zabel Association and Mateja Kurir and held at Museum of Architecture and Design in Ljubljana, where she presented a paper on Manfredo Tafuri. Teresa has recently become Professor of Research in Architecture at London South Bank University, moving there from Leeds Beckett University. The area where London South Bank University is situated is highly typical of the processes currently underway in London and especially south of the Thames. Once a relatively destitute area of the capital, it is now quickly transforming into one of the most expensive areas of the metropolis. Foreign investors, CEOs and students often live a stoneās throw from social housing tenants unsure of how long they will still be permitted to stay and when their estates will be redeveloped by private investors. A very suitable background for our discussion on criticality, gentrification and the understanding of the role of the architect today
NanoÅ”enje elektriÄnom iskrom za popravak alata
The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined.NanoÅ”enje elektriÄnom iskrom postupak je za navarivanje tvrdih metalnih slitina, npr. karbida i stelita, na povrÅ”inu novih ili starih elemenata strojeva. U tom postupku visoka struja provodi se kroz oscilirajuÄu elektrodu i supstrat na vrlo kratko vrijeme. U Älanku opisan je postupak i odreÄeni su debljina nanesenog sloja, kemijski sastav, stupanj mijeÅ”anja i hrapavost sloja
Mechanochemical synthesis of NaNbO3, KNbO3 and K0.5Na0.5NbO3
Mechanochemical synthesis of the K0.5Na0.5NbO3 solid solution (KNN) is studied. In order to explore the mechanochemical interactions between the constituents in the Na2CO3 - K2CO3 - Nb2O5 system, NaNbO3 and KNbO3 as the boundary compositions of the KNN solid solution are also studied. It has been shown that NaNbO3 can be prepared by a single-step mechanochemical synthesis, while in the case of K2CO3 and Nb2O5, and Na2CO3, K2CO3 and Nb2O5 mixtures, only amorphisation occurs even after prolonged milling
Electrospark deposition for die repair
The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined
Procjena mikrostrukture alatnog Äelika za hladni rad nakon pretaljivanja pulsirajuÄim laserom
The aim of this study is the investigation of micro-structural behaviour of a Mat. No. 1.2379 (EN-X160CrMoV121; AISI D2) cold work tool steel after remelting with a precise pulsed Nd:YAG laser. The investigated steel is one of the most hard to weld tool steels, due to large amount of alloying elements. The analysis was done on single spots remelted with specific laser pulse shape and parameters, assuring crack-less solidification. Re-solidifi ed areas were investigated with microscopy, hardness measurements, X-ray spectroscopy and diffraction method. Laser treatment causes rapid solidification leading into a formation of a fine dendritic microstructures containing high amount of retained austenite causing a significant decrease of hardness.Namjena ove studije je ispitivanje ponaÅ”anja mikro strukture alatnoga Äelika za rad na hladno Mat. No.1.2379 (ENX160CrMoV121; AISI D2) po pretaljivanju s preciznim pulsiranim Nd:YAG laserom. Zbog velike koliÄine legirnih elemenata istraživani materijal spada u grupu vrlo teÅ”ko zavarljivih alatnih Äelika. Analiza je provedena na pojedinim pretaljenim toÄkama koriÅ”tenjem specifi Änog oblika i parametara laserskog impulsa koji osiguravaju skruÄivanje bez pukotina. Pretaljena podruÄja su ispitivana mikroskopom, mjerenjem mikro tvrdoÄe, rendgenskom spektroskopijom i defrakcijskom metodom. Tretman laserom uzrokvao je brzo skruÄivanje koja dovodi do formiranja fi ne dendritiÄke strukture s velikim udjelom zaostalog austenita Å”to uzrokuje bitno smanjivanje tvrdoÄe
Influence of the Deep Cryogenic Treatment on AISI 52100 and AISI D3 Steelās Corrosion Resistance
The effect of deep cryogenic treatment (DCT) on corrosion resistance of steels AISI 52100 and AISI D3 is investigated and compared with conventional heat-treated counterparts. DCTās influence on microstructural changes is subsequently correlated to the corrosion resistance. DCT is confirmed to reduce the formation of corrosion products on steelsā surface, retard the corrosion products development and propagation. DCT reduces surface cracking, which is considered to be related to modified residual stress state of the material. DCTās influence on each steel results from the altered microstructure and alloying element concentration that depends on steel matrix and type. This study presents DCT as an effective method for corrosion resistance alteration of steels
Lasersko reparaturno zavarivanje alata s razliÄitim oblicima impulsa
Repair welding of cold-work tool steels with conventional methods is very difficult due to cracking during remelting or cladding and is generally performed with preheating. As an alternative, repair welding with laser technology has recently been used. This paper presents the influence of different pulse shapes on welding of such tools with the pulsed Nd:YAG laser. Repair welding tests were carried out on AISI D2 tool steel, quenched and tempered to hardness of 56 HRc, followed by microstructural analysis and investigation of defects with scanning electron microscopy. Test results suggest that it is possible to obtain sound welds without preheating, with the right selection of welding parameters and appropriate pulse shape.Reparaturno zavarivanje alatnih Äelika za rad na hladno konvencionalnim metodama je vrlo teÅ”ko zbog pukotina nastalih tokom pretaljivanja i navarivanja i opÄenito vrÅ”i se uz predgrijavanje. U posljednje vrijeme se kao alternativna metoda koristi reparaturno zavarivanje upotrebom laserske tehnologije. Ovaj rad predstavlja utjecaj razliÄitih oblika impulsa na zavarivanje alatnih Äelika s pulsnim laserom Nd:YAG. Reparaturno zavarivanje testirano je na alatnom Äeliku AISI D2, termiÄki obraÄenim na tvrdoÄu 56 HRc, poslije Äega je provedena analiza mikrostrukture i traženje defekata skeniranjem elektronskim mikroskopom. Rezultati testiranja sugeriraju da je moguÄe izvesti dobre zavare bez predgrijavanja pravilnim izborom parametara zavarivanja i odgovarajuÄeg oblika impulsa
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